Ever find a massive hidden junction box buried behind old wallpaper?

Finding a buried four-gang box like that is basically the holy grail of 'previous owner' nightmares. You're looking at a massive violation of **NEC 314.29**, which explicitly states that boxes must be accessible without removing any part of the building finish. It happens all the time during mid-century or 80s 'remasters' where someone decided a blank plate looked ugly and just slapped drywall or wallpaper over it becasue they didn't want to deal with the visual clutter.

You’ve really only got two legitimate paths forward here if you want to keep it legal and safe. The easiest fix is installing a large access panel or a custom blank cover. If they're repapering, you can paint the cover to match or even paper over the plate itself, but you absolutely have to leave those screws visible so someone can find it again without a sledgehammer. Burying it again is just asking for a fire down the road when one of those loose neutrals starts arcing in a sealed cavity. Rerouting everythign is the 'proper' way to handle it, but it's a total nightmare in these old structures. You're talking about tracing every single one of those circuits back to a reachable point and pulling new home runs or setting up new, accessible junctions. In an old apartment building, those wires are often stapled or fished in ways that make a simple pull impossible. Unless the client's budget is bottomless, an access panel is usally the way to go. Take the time to kill the power and go through that box wire by wire. If it's as packed as you say, the **box fill** capacity is probably way over the limit. Check for any scorched insulation or loose wire nuts. Those old colored nut assortments sometimes lose their grip over decades of thermal expansion and contraction. Tighten everything down, or better yet, swap them out for some modern lever connectors if you have the room, before you seal it behind a panel.

How do you guys even spot these things without tearing the whole place apart? Is there like a stud finder that picks up on the metal boxes, or do you just listen for a hollow sound?

Also, you mentioned those lever connectors—are those basicly the Wago things I see people talking about? I've only ever used standard wire nuts on small stuff, so I'm wondering if they really save that much space in a crowded four-gang. If that box is alredy packed, it seems like adding anything new would just make it harder to close up.

Wagos are a total game changer for box fill. Those bulky wire nuts require you to twist and fold a massive knot of copper, but lever connectors let the wires lay much flatter. In a crowded junction like that, it’s often the only way to actualy get a cover plate on without crushing everything. If you're hunting for more, check for outlets that have three or four cables but don't seem to feed anything nearby. Usually, the 'hidden treasure' is directly upstream or downstream from those. I’ve also had luck using a cheap non-contact voltage tester; sometimes you can pick up the field through thin drywall if the load is high enugh.

If it's a metal box, a strong magnet can be your best friend for finding these 'buried treasures' without poking holes every six inches. I ussually just run a neodymium magnet along the wall where things don't make sense circuit-wise.

Also, keep an eye out for any wierd bumps in the wallpaper. Sometimes the heat from a crowded, over-filled box actualy causes the glue to fail or the paper to discolor over time. It’s like the house is trying to tell you where the fire hazard is. If you find one, there's usually a sister box somewhere else on the same floor.